Paint colorant product and method

ABSTRACT

A neutral paint colorant has a composition comprising approximately 7.0% Color Index Pigment Yellow 42, 2.4% Color Index Pigment Red 101, and 4.0% Color Index Pigment Black 7. A pre-blended mixture of the neutral colorant and a paint base can be blended with a first paint to form a second paint having substantially the same hue and value (lightness) as the first paint, but a lower chroma (brightness).

BACKGROUND

1. Field

The present invention relates generally to architectural paints and, inparticular, to architectural paint colorants.

2. Description of the Related Art

Architectural paint (“house paint”) is commonly provided in variouscolors. Paint color groups have been developed to provide a selection ofarchitectural paint colors to consumers.

Paint colors are sometimes referenced with respect to systems forarranging and describing color, generally referred to as color-ordersystems. One well-known color-order system is the Munsell system.According to the Munsell system, all possible colors are characterizedby three attributes: hue, value, and chroma. Hue is the attribute ofcolor which is commonly described by words such as “red,” “yellow,”“green,” “blue,” “purple,” etc. Value is the attribute of color which isdescribed by the words “light,” “dark,” etc. Chroma is the attribute ofcolor which is described by the words “bright,” “dull,” etc. Forexample, the colors of a tomato and a brick may be equal in hue andvalue, yet the colors are not identical. The difference is that thetomato is brighter, having a higher chroma.

Munsell color space is a three-dimensional space including anddescribing visual relationships between colors. This color space isbased on a collection of actual physical samples arranged so thatadjacent samples represent distinct intervals of visual colorperception. Although based on physical samples, Munsell color space istheoretically capable of describing all possible colors. According tothe Munsell system, color space is described with respect to threedimensions: hue, value, and chroma. Theoretically, the Munsell locationof every possible color can be described by three coordinates,corresponding to the hue, value, and chroma of the given color. Althoughin theory Munsell color space is capable of describing all colors, it isunderstood that it may not be possible to create physical samples of allof the colors which could theoretically fit within Munsell color space.In particular, not all theoretical colors within the perceived Munsellcolor space can be made into paints.

Within Munsell color space, a vertical axis, known as the value axis,represents color value. In other words, the value (lightness/darkness)of color is determined by the vertical position within color space.Color becomes lighter as the vertical position increases. The hue ofcolor is determined by the angular position about the vertical valueaxis. The various hues, i.e., shades of red, yellow, green, blue,purple, etc., are represented by vertical planes extending radially fromthe value axis. Moreover, every angular position about the axis, from 0°to 360°, represents a different hue. The chroma (brightness/dullness) ofcolor is determined by the radial distance from the value axis. Color isdull (gray) near the axis and becomes brighter, or more “chromatic,” asthe radial distance from the value axis increases.

The Munsell system is one of a number of color-order systems based onactual physical samples. Another class of color-order systems are notbased on physical samples. One of the most important of these systems isthe CIE System (Commission International de l'Eclairage or InternationalCommission on Illumination). The premise of the CIE System is that thestimulus for color is provided by a proper combination of a source oflight, an object, and an observer. The CIE System describes color withreference to a standard source of illumination and a standard observer.

One widely used non-linear transformation of the CIE System is CIELAB,an opponent-type space in which color is described by the threecoordinates L, a, and b. In CIELAB space, L is the lightness of color(similar to Munsell value), a is a redness-greenness coordinate, and bis a yellowness-blueness coordinate. Several color-order systems existwithin CIELAB space. One such color-order system is D65 CIELAB.

Paints of various colors are generally formed by mixing one or moreliquid paint colorants with a paint base. Paint color can be varied byusing a different combination of paint colorants, or by changing theconcentration of one or more of the colorants in the paint. Paintcolorants are formed by blending one or more pigments into what theindustry refers to as a “grinding liquid,” a liquid grinding medium. Thecoloring power of a paint colorant can be varied by changing the pigmentconcentrations of the constituent pigments in the colorant.

Existing methods for producing paints for customers at a retail sitecommonly utilize a mixing device having a plurality of spouts, eachadapted to eject one or more drops of a particular paint colorant into apaint base. Accordingly, a customer may select a desired quantity ofpaint having a desired paint color. The desired paint color has knownratios of various paint colorants to a paint base. Typically, a painttechnician will operate the mixing device so as to mix the variousquantities of the constituent paint colorants with a quantity of thepaint base to produce the desired quantity of the selected paint color.A limitation of this method is that it may be difficult to accuratelyproduce the selected paint color. The smallest quantity of any colorantthat the mixing device can eject is a drop of about {fraction (1/96)} ofan ounce. Some mixing devices are limited to drops of {fraction (1/48)}of an ounce. Thus, the amount of any given constituent colorant in theproduced paint will be a multiple of drops. However, it may be desirableto blend an amount of a particular colorant which is not exactly equalto a multiple of drops. This “one-drop” limitation of the mixing devicecauses some inherent imprecision in the mixing of colorants, which mayresult in the produced paint having a color which is slightly differentthan that which was selected by the customer.

SUMMARY

Accordingly, it is a principle object and advantage of the presentinvention to overcome some or all of these limitations and to provide aspecialized paint colorant facilitating the accurate production of paintcolors throughout a given architectural paint color space.

The present invention provides a “neutral paint colorant” to aid in thedevelopment of paint colors throughout color space. In particular, theneutral paint colorant, or simply neutral colorant, may be added to apaint to decrease the paint's chroma while maintaining its huesubstantially constant. Advantageously, the neutral colorant may beadded to highly chromatic colors to develop duller colors that may bemore suitable for some purposes. This is especially useful in thearchitectural paint environment in which duller, less chromatic colorsare used more often than brighter, more chromatic colors.

One may readily determine the colorant compositions of the architecturalpaint colors developed with the aid of the neutral colorant of theinvention. Each paint color comprises a mixture of prime colorants,neutral colorant, and paint base. The ratios of each of theseconstituents to the whole mixture are determined as described below. Thecolorant compositions of various paint colors may be recorded in astorage medium for use at a retail site. Advantageously, a system isimplemented which permits a consumer to select a paint color and thenretrieves the composition of the selected paint color. The compositionmay be fed to an automated paint production apparatus or may betransmitted to a paint technician who will produce the selected paintcolor.

In one aspect, the present invention provides a method of forming aneutral paint colorant, comprising the following steps: A first colorantis blended with a paint base to form a paint having a chromasubstantially equal to zero. A quantity of one of the first colorant orthe paint base is added to the paint, to vary the value of the paint.The chroma of the paint is then measured. If the chroma of the paint isnot substantially equal to zero, one or more offsetting colorants areadded to the paint to reduce the chroma of the paint so that it issubstantially equal to zero. The neutral paint colorant comprises amixture of the first colorant and the offsetting colorants. Thecomposition of the neutral colorant is determined by the relativeamounts of the first colorant and the offsetting colorants which are inthe paint.

In another aspect, the present invention provides a paint colorantcomprising a mixture of pigments blended with a grinding liquid. Thecolorant is configured to be added to a first paint to form a secondpaint, wherein the chroma of the second paint is less than the chroma ofthe first paint, and the hue of the second paint is substantially thesame as the hue of the first paint.

In another aspect, the present invention provides a paint colorantcomprising a mixture of pigments blended with a grinding liquid. Thecolorant is configured to be added to a first paint base to form a firstpaint. The first paint has the property that when the first paint isadded to a second paint made from the same paint base as the firstpaint, a third paint is formed, wherein the chroma of the third paint isless than the chroma of the second paint, and the hue and value of thethird paint are substantially the same as the hue and value of thesecond paint. Advantageously, the “component ratios” of the variousconstituent colorants to the base in the third paint can be readilydetermined from the quantities of such colorants and the base in thefirst and second paints. Such component ratios may then be usedsubsequently to recreate the paint color of the third paint.

In another aspect, the present invention provides a method of producinga paint, comprising the steps of blending a mixture of pigments with agrinding liquid to form a neutral paint colorant, adding the neutralpaint colorant to a first paint base to form a first paint, and adding avolume of the first paint to a volume of a second paint to form a thirdpaint. The neutral paint colorant has the property such that the chromaof the third paint is less than the chroma of the second paint, and thehue of the third paint is substantially equal to the hue of the secondpaint. Further, the addition of the neutral paint colorant to the firstpaint base may be controlled so that the first paint has a valuesubstantially equal to the value of the second paint.

In another aspect, the present invention provides a paint colorantcomprising 6.3% to 7.7% Color Index Pigment Yellow 42, 2.16% to 2.64%Color Index Pigment Red 101, and 3.6% to 4.4% Color Index Pigment Black7. In a narrower aspect, the paint colorant comprises 7.0% Color IndexPigment Yellow 42, 2.4% Color Index Pigment Red 101, and 4.0% ColorIndex Pigment Black 7. The remainder of the paint colorant comprisescomponents other than pigments, such as a grinding liquid.

In another aspect, the present invention provides a method of producinga neutral paint colorant, comprising the steps of blending Color IndexPigment Yellow 42, Color Index Pigment Red 101, and Color Index PigmentBlack 7 together to form a pigment mixture, and blending the pigmentmixture into a grinding liquid to form a paint colorant. The paintcolorant has a composition of 6.3%-7.7% Color Index Pigment Yellow 42,2.16%-2.64% Color Index Pigment Red 101, and 3.6%-4.4% Color IndexPigment Black 7.

In another aspect, the present invention provides a method of creating apaint, comprising the steps of selecting a source paint comprising amixture of paint colorants with a first paint base, blending a neutralpaint colorant with a second paint base to form a neutral paint, andblending the neutral paint with the source paint to form an outputpaint. The neutral colorant comprises 6.3% to 7.7% Color Index PigmentYellow 42, 2.16% to 2.64% Color Index Pigment Red 101, and 3.6% to 4.4%Color Index Pigment Black 7. The first and second paint bases areidentical. The hue and value of the created output paint aresubstantially equal to the hue and value of the source paint, and thechroma of the created output paint is less than the chroma of the sourcepaint.

In another aspect, the present invention provides a device for blendingpaint colorants with a paint base to create an architectural painthaving a desired hue, value, and chroma. The device comprises aplurality of spouts adapted to eject a paint colorant, wherein one ofthe spouts is adapted to eject a neutral paint colorant. In oneembodiment, the neutral paint colorant comprises 6.3% to 7.7% ColorIndex Pigment Yellow 42, 2.16% to 2.64% Color Index Pigment Red 101, and3.6% to 4.4% Color Index Pigment Black 7.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description having reference to the attachedfigures, the invention not being limited to any particular embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical illustration of a theoretical color space;

FIG. 2 is a perspective view of the theoretical color space of FIG. 1;

FIG. 3 is a horizontal, i.e., uniform value, cross-sectional view of thetheoretical color space of FIG. 1;

FIG. 4 is a uniform hue plane of the theoretical color space of FIG. 1;

FIG. 5 is a uniform hue plane of the theoretical color space of FIG. 1,illustrating the most chromatic colors across the entire value range;and

FIG. 6 is a uniform hue plane of the theoretical color space of FIG. 1,illustrating the chroma-shifting effect of adding the neutral paintcolorant of the present invention to a paint.

DETAILED DESCRIPTION

In general, any of a variety of color languages may be used to describecolor. These languages have been developed to describe qualities whichare visually perceived. The teachings and claims of this invention aredirected toward that which is visually perceived, which may be describedby the use of any color language. Although the invention is describedwith reference to a particular color language system described below,the invention is not intended to be limited to that context. In otherwords, it is contemplated that other color language systems could alsobe used to describe the present invention.

The present invention recognizes that it is useful to describearchitectural paint colors with reference to hue, value, and chroma ascontemplated by a theoretical color system. To describe the invention,it will be helpful to provide a context for the discussion of color,including a three-dimensional color space model.

An appropriate theoretical three-dimensional color space is graphicallyillustrated in FIG. 1. A vertical value axis 20 is shown. The value ofcolor, i.e., the lightness or darkness of color, is determined by thevertical position within the color space. Color becomes lighter as thevertical position increases. The hue of color, i.e., the quality ofcolor which is described by the words “red,” “yellow,” etc., isdetermined by the angular position about value axis 20. The chroma,i.e., brightness, of color is determined by the radial distance fromvalue axis 20. Chroma is equal to 0 at the value axis 20. The colorspace is described below with respect to each of the individualdimensions value, hue, and chroma.

According to the system, color has a finite value (lightness) range.Thus, as shown in FIG. 1, value axis 20 has a finite length. Bydefinition, the minimum value of color is 0, represented at the bottompoint 22 of value axis 20, and the maximum value of color is 100,represented at the top point 24 of value axis 20. Value axis 20represents varying lightness shades of gray, with the darker grays beingnearer to the bottom of the axis and the lighter grays being nearer tothe top. The bottom point 22 of value axis 20 has zero lightness andcorresponds to pure black, the darkest color. Moreover, only pure blackhas a value equal to 0. Thus, the color space converges at point 22 ofvalue axis 20. The top point 24 of value axis 20 has maximum lightnessand corresponds to pure white, the lightest color. Moreover, only purewhite has a value equal to 100. Thus, the color space converges at point24 of value axis 20. Due to the convergence of the color space at theendpoints 22, 24 of value axis 20, the color space has a cocoon-likeshape, as shown in FIG. 2.

According to the system, color also has a finite hue range. Color hue islimited to the angular positions spanning 0° to 360° about value axis20. As the angular position about the axis changes, color transitionsthrough a fixed sequence of hues. FIG. 3 shows a horizontalcross-section of the color space, intersecting value axis 20 between theendpoints 22 and 24 shown in FIG. 1. In other words, FIG. 3 shows aplane within the color space, having a uniform value between 0 and 100.As shown in FIG. 3, in the counter-clockwise direction about the valueaxis, hue transitions through the following generalized sequence: red,pink, violet, indigo, purple, blue, aqua, green, yellow, and orange. Ofcourse, the colors indicated in FIG. 3 will be lighter or darker fordifferent values between 0 (point 22) and 100 (point 24).

In addition to indicating variations in hue, the planar cross-section oftheoretical color space represented by FIG. 3 also illustrates chromaticvariations in the space. Color becomes brighter as the distance from thevalue axis 20 increases. Positions far from the value axis are verybright, or chromatic, while positions near the value axis are dull andmore grayish. In theory, there is no limit to the possible chroma(brightness) of color having any given hue. However, in practice, colorhas a limited range of chroma, due to the fact that colors having chromabeyond a certain limit have not been discovered. In particular, for anygiven value and hue, color has a limited known chroma range. The word“known” is used to indicate that, for a given hue and value, higherchroma are not known to exist. The known chroma range is from 0 at thevalue axis 20 to an outer radial limit. The outer radial limit of theknown chroma range varies for different values and hues. For example, alight yellow has a greater maximum known chroma than does a darkeryellow. A dark red has a different maximum known chroma than does alight blue.

FIG. 4 illustrates the varying known chroma range of color in thetheoretical color space. FIG. 4 shows a uniform hue plane of the space,i.e., a “slice” of color space corresponding to a single hue. Inparticular, a vertical plane is shown passing through the value axis 20and extending radially outward therefrom. This is essentially a knownchroma range profile for a given hue. The profile shown in FIG. 4 istypical of most hues within the color space. As shown, the uniform hueplane has a straight edge, corresponding to the value axis 20, and acurved edge 28 corresponding to the highest known chroma for any givenvalue. For example, consider a point A on the curved edge 28. Point Ahas a value V_(A) and a chroma C_(A). Thus, at the value V_(A), thehighest known chroma within the displayed hue plane of the space isC_(A). Within the uniform hue plane, the known chroma range varies withvalue. At the bottom of the value axis, the known chroma range convergesat the point 22. As the value increases, the known chroma range becomeslarger. The maximum known chroma range within the displayed hue plane isat the value V_(M), at which the known chroma ranges from zero at thevalue axis to C_(M) on the line 28. The point M corresponds to thebrightest color having the hue of the uniform hue plane. As the valueincreases above V_(M), the known chroma range decreases. At the top ofthe value axis, the known chroma range converges at the point 24. It isunderstood that in practice it may not be possible to create all of themore chromatic colors of a given hue, particularly for architecturalpaints.

The present invention provides a “neutral paint colorant,” or “neutralcolorant,” which may be used, as described below, to decrease a paint'schroma while maintaining the paint's hue substantially constant. In anarrower aspect, the neutral paint colorant may be used to decrease apaint's chroma while maintaining the paint's hue and value substantiallyconstant. The term “neutral” indicates that the neutral colorant isachromatic, i.e., has a chroma approximately equal to zero. This meansthat the color is on or near the value axis 20. Moreover, when theneutral colorant is added to a paint base, the resulting paint is alsoachromatic. The value of the resulting paint depends on theconcentration of the neutral colorant therein. As the concentration ofneutral colorant decreases, the value increases (assuming the paint baseis white).

The neutral colorant is preferably formed according to the followingprocess: Initially, a first paint colorant is chosen, which when blendedwith a particular quantity of a paint base forms a paint havingsubstantially zero chroma. Preferably, the chroma is preferably lessthan 0.15, more preferably less than 0.1, and even more preferably lessthan 0.05. The chroma may change as the value of the output paint colorchanges, i.e., as the relative proportions of base and first colorantare varied. A suitable paint colorant to begin with is black, especially“lamp-black,” because it has a very low chroma. Hereinafter, the term“colorant” is understood to mean a mixture of a pigment with a grindingliquid. Black also has a low value. The value may be gradually increasedby adding incremental quantities of a white paint base. Alternatively,the value may be decreased by adding incremental quantities of moreblack colorant.

After choosing a first paint colorant, it is blended with a paint baseso that it has a first value at which chroma is substantially zero, asmentioned above. The value is then varied by adding one of a quantity ofpaint base or more of the first paint colorant, to form a differentoutput paint color. Suppose the value is varied to a second value. Thechroma of the output paint color is measured. If the chroma issubstantially zero, the first colorant has maintained its neutralityalong the value range defined between the first and second values. Ifthe chroma is not substantially zero, the color has shifted from thevalue axis 20. For example, the color of lamp-black colorant may shiftto a slightly chromatic blue. This color shift is caused by the factthat lamp-black colorant has some blue in it. The color shift can becompensated by the addition of one or more offsetting colorants. In theexample given, the shift toward blue may be compensated by addingdifferent quantities of, for example, red and yellow colorants, so thatthe color shifts back to the value axis 20. The targeted neutralcolorant will ultimately be a combination of the first colorant and theoffsetting colorants which are added to compensate for such colorshifts. Thus, the composition of the neutral colorant of the inventionevolves with the addition of the first and the offsetting colorants, thecomposition being the proportionate amounts of the constituentcolorants.

The process is then repeated. Another quantity of one of the base or thefirst colorant is added to the paint so that it has a third value. Thechroma is again measured. If the chroma is zero, the evolving neutralcolorant has maintained its neutrality across the value range defined bythe highest and lowest of the first, second, and third values. If thechroma is not zero, offsetting colorants are again added as above tocompensate for the color shift. Optionally, the same offsettingcolorants as before are used, so that the final composition of theneutral colorant has a small number of constituent colorants. Theprocess is then repeated again. In this manner, the composition of theneutral colorant is repeatedly adjusted for a multitude of values(steps) across a desired overall value range, defined as the value rangebetween the highest and lowest values at which the composition of theneutral colorant is adjusted as described above. The process preferablyincludes at least three steps. As more steps are taken, the compositionof the neutral colorant evolves to more precisely maintain neutralityacross the overall value range. At each step, offsetting colorants areadded if the chroma of the paint is greater than a desired tolerance.The desired tolerance is preferably 0.15, more preferably 0.1, and evenmore preferably 0.05.

The above-described process results in a neutral colorant that maintainsits neutrality across a desired overall value range. The combination ofconstituent colorants which comprise the neutral colorant may be chosenarbitrarily, but should have the effect of compensating any shifts incolor caused by changes in the value of the paint color. Each step inthe process may require a different adjustment of the constituentcolorants, as compared to previous steps. For example, the color shiftof the evolving neutral colorant may be greater at higher values than atlower values, requiring more of the offsetting colorants to be added. Inaddition, it may be necessary to add a greater quantity of one or moreof the offsetting colorants to compensate for a color shift. After asuitable number of steps have been taken to arrive at a particularcomposition of the neutral colorant, the neutral colorant is preferablytested again throughout the entire color range.

As mentioned, the neutral colorant comprises a mixture of the firstcolorant and the offsetting colorants. The composition of the neutralcolorant is determined by the relative amounts of the first colorant andthe offsetting colorants which are in the paint. The composition of theneutral colorant may be expressed by the mass ratios of each of theconstituent colorants to the total mass of the mixture of colorants. Theratio of the first colorant to the total mixture is equal to the totalamount of the first colorant in the paint divided by the total amount ofthe first colorant and the offsetting colorants in the paint. The ratioof each of the offsetting colorants to the total mixture is equal to thetotal amount of the individual offsetting colorant in the paint dividedby the total amount of the first colorant and the offsetting colorantsin the paint.

The above-described process has been conducted beginning with a colorantcomprising Color Index Pigment Black 7. As quantities of paint base areincrementally added to this colorant, the paint color shifts towardblue. Suitable first and second offsetting colorants comprise ColorIndex Pigment Yellow 42 and Color Index Pigment Red 101. Thus, accordingto one embodiment, the composition of the neutral colorant is, by mass,6.3% to 7.7% Color Index Pigment Yellow 42, 2.16% to 2.64% Color IndexPigment Red 101, and 3.6% to 4.4% Color Index Pigment Black 7. Thesepigments are well-known in the art and are available in powder form. Theremainder of the neutral colorant is a grinding liquid. Preferably, theneutral colorant has a composition comprising approximately, by mass,7.0% Color Index Pigment Yellow 42, 2.4% Color Index Pigment Red 101,and 4.0% Color Index Pigment Black 7. Such a neutral colorant has beenfound to maintain its neutrality (approximately zero chroma) across alightness range of approximately 50-95.

The above-described embodiment of the neutral colorant may be formed byfirst blending the above-mentioned pigments together, before adding themto a grinding liquid. In order to achieve the above-mentioned ratio ofpigments in the liquid colorant, the powder form pigments may be blendedin the following approximate ratio, by mass: 52.239% Color Index PigmentYellow 42, 17.910% Color Index Pigment Red 101, and 29.851% Color IndexPigment Black 7. These percentages may be varied somewhat withoutstraying from the scope of the invention. Then, the mixture of pigmentsis added to a volume of a grinding liquid to produce the neutralcolorant. The volume of the grinding liquid is preferably such that thepercentage masses of the individual pigments in the liquid colorant areapproximately as listed above. Thus, the amount of grinding liquid ispreferably such that the percentage mass of Color Index Pigment Yellow42 is approximately 7.0%, the percentage mass of Color Index Pigment Red101 is approximately 2.4%, and the percentage mass of Color IndexPigment Black 7 is approximately 4.0%.

A suitable grinding liquid for the purposes of the invention is amixture of water, glycol, acrylic resin, and dispersants, i.e., wettingagents. Once the pigments are suspended in the grinding liquid, a sandmill may be used to finely blend the colorant. Afterwards a versator maybe used to remove any air bubbles in the colorant. The use of sand millsand versators is well known in the art.

According to a method described below, the neutral colorant of theinvention may be used to produce paint colors throughout the theoreticalcolor space. Moreover, for each paint color created, it is possible todetermine the ratio of constituent components therein, i.e., therelative amounts of neutral colorant, other colorants, and paint base.Advantageously, this data may be compiled and used at a retail site toprepare paints of a desired color upon request. This aspect of theinvention is described in further detail below.

According to a method of the present invention, the neutral colorant maybe added to a paint to advantageously reduce the paint's chroma withoutappreciably varying the paint's hue or value. Initially, a source paintis selected, wherein it is desired to produce one or more paints havinghue and value substantially equal to, and chroma less than, the hue,value, and chroma, respectively, of the source paint. The source paintcomprises a mixture of a paint base with one or more of a set of “primecolorants,” i.e., various colorants other than the neutral colorant.Such prime colorants may comprise combinations of various pigments otherthan those comprising the neutral colorant. A volume of the neutralcolorant is then added to a paint base of the same type as the paintbase of the selected source paint, to form a “neutral paint.” The volumeof neutral colorant is controlled so that the value (lightness) of theneutral paint is matched to the value of the source paint. In general,the addition of a relatively small amount of neutral colorant to thepaint base results in a relatively high value (light) neutral paintcolor. The value of the neutral paint color decreases (becomes darker)as more neutral colorant is added. Preferably, the neutral colorant isblended with the paint base in small increments until the value of theneutral paint color is matched to the value of the source paint color.The values of the source paint and neutral paint may be measured, andhence may be matched, by using a spectrophotometer, a device which iscapable of scanning a color and determining its color coordinates, suchas its hue, value, and chroma or its CIELAB coordinates. One type ofspectrophotometer is a SpectroEye™, manufactured by Gretag Macbeth ofNew Windsor, N.Y., which provides D65 CIELAB coordinates of a scannedcolor.

Once the value of the neutral paint color is matched to that of thesource paint color, a volume of the neutral paint may be added to avolume of the source paint to create a paint having a lower chroma thanthat of the source paint, but substantially the same hue and value. Thechroma of the created paint will continue to decrease as more of theneutral colorant is added. This is because the achromatic neutralcolorant tends pull the color toward the value axis 20 (FIG. 1). Also,the degree of chroma reduction can be increased by starting with a lowerinitial volume of the source paint. In this manner, the addition of theneutral colorant to highly chromatic paints facilitates the developmentof paint colors throughout color space.

Alternatively, the above-described neutral colorant may be blendeddirectly with the source paint. In other words, the step of preparing aneutral paint may be skipped. In this case, the resultantly createdpaint will have substantially the same hue as the source paint, but alower chroma and, probably, a different value. The value of the paintwill change if, as will often be the case, the value of the neutralcolorant itself is different than that of the source paint. Unlike theprocess described above, in this case the neutral colorant is not firstblended with a base and matched to the value of the source paint priorto being added thereto. The difference in value between the neutralcolorant and the source paint will cause the value of the paint toshift. On the other hand, if the value of the neutral colorant itself isequal to that of the particular source paint, then there is unlikely tobe any value shift.

FIGS. 5 and 6 illustrate the use of the neutral colorant. These figuresboth show a uniform hue plane of the theoretical color space describedabove. In FIG. 5, the outer radial portion of the uniform hue plane isindicated by section 32, which represents the more chromatic colors forthe entire value range of the shown uniform hue plane. Paint colorswithin section 32 are generally formed by adding prime colorants topaint bases. Referring to FIG. 6, a point 34 represents the color of ahighly chromatic source paint. A volume of neutral paint may be added tothe source paint. It is understood that the neutral paint contains amixture of the neutral colorant with the same type of paint base as inthe source paint, such that the neutral paint has a matching value asdescribed above. It is further understood that a set of paints having auniform value, such as the paints represented by line 42, can be and arepreferably formed from the same type of paint base. The addition of avolume of neutral paint to the paint represented by point 34 causes thecolor to shift along line 42 to point 36. Point 36 represents a paintcolor having substantially the same hue and value as the paint color ofpoint 34. However, the paint color of point 36 is somewhat lesschromatic. If an additional amount of the neutral paint is added to thepaint represented by point 36, the color shifts further along line 42 topoint 38. Point 38 represents a paint color having substantially thesame hue and value as the paint colors of points 34 and 36. However, thepaint color of point 38 is somewhat less chromatic than that of point36. Similarly, the addition of more of the neutral paint shifts thecolor further along line 42 to point 40. The neutral paint may be addedto highly chromatic colors of various hues and values throughout thecolor space.

In this manner, the color space can be filled in from the most chromaticcolors inward to the value axis 20. Note that this process mayalternatively begin with a paint color which is not highly chromatic,i.e., not within section 32 of FIG. 5.

As mentioned above, for each paint color created in the above-describedmanner, such as the paint colors represented by the points 36, 38, and40 in FIG. 6, the component ratios thereof (ratios of the various paintcolorants, including the neutral paint colorant of the presentinvention, to the paint base) can readily be determined. For example,suppose the process begins with one gallon of Paint A, which is known tocontain six ounces of Prime Colorant X mixed with Base Y. Suppose thatthe neutral colorant of the present invention is mixed with a volume ofBase Y to develop a “neutral paint” having the same value as Paint A.Suppose further that one gallon of the neutral paint contains fourounces of the neutral colorant. If one gallon of Paint A is blended withone gallon of the neutral paint, there is formed two gallons of paintwhose color has a lower chroma than that of Paint A. This product paintis referred to herein as Paint B. Two gallons of Paint B contains sixounces of Prime Colorant X and four ounces of the neutral colorant.Thus, the component ratios of Paint B can be easily determined. Onegallon of Paint B comprises three ounces of Prime Colorant X, two ouncesof the neutral colorant, and the remainder Base Y.

In this manner, the component ratios may be determined for all of thepaint colors within the color space. In fact, the present inventors havecreated a database of about 50,000 architectural paint colors spanningthe known color space, for each of which paint colors the componentratios are known. Advantageously, a desired quantity of a paint having aselected paint color can easily be produced for a customer at a retailsite from the component ratios of that particular paint color.Accordingly, the paint colors in the database may be displayed at aretail site to customers. The component ratios for all the paints in thedatabase can be stored on a storage medium, such as a lookup table on acomputer memory. Once a customer decides to purchase a selected paintfrom the database, the component ratios for the selected paint color maybe read from the storage medium. An in-store system may be automated toproduce the desired quantity of paint having the selected paint color,or the system may alternatively be configured to send the componentratios thereof to a paint technician to produce the desired paint.

Advantageously, the neutral colorant of the present invention makes iteasier to more accurately produce, at a retail site, a relatively smallquantity of paint having a desired paint color, as compared to prior artmethods. This is due to the fact that the neutral colorant comprises amixture of pre-blended pigments with a grinding liquid. In particular,these pigments are pre-blended in precisely the necessary ratios to havethe property that the neutral colorant may be added to a paint withoutsubstantially changing the paint's hue. These pigments are not processedas separate paint colorants to be mixed at the retail site, as in theprior art. Further, the neutral colorant advantageously avoids theproblems associated with the “one-drop” limitation described earlier.This is because any amount of drops of the neutral colorant may be addedto a paint without substantially changing the paint's hue.

As mentioned above, the neutral paint has the desired property ofdecreasing the chroma of a source paint to which the neutral paint isadded without appreciably varying the source paint's hue or value. Also,the neutral paint is formed by blending the neutral colorant of theinvention with an available paint base. With regard to the specificallymentioned embodiment of the neutral colorant, comprising 6.3%-7.7% ColorIndex Pigment Yellow 42, 2.16%-2.64% Color Index Pigment Red 101, and3.6%-4.4% Color Index Pigment Black 7, optimum results have been foundby combining the neutral colorant with white or tint bases, pastelbases, and midtone bases. However, the combination of this particularneutral colorant with clear or deep bases or with bases having a largeproportion of machine-tinted colorants has been found to result in abrown color which is unsuitable for the goal of decreasing chromawithout appreciably varying hue or value. In general, this embodiment ofthe neutral colorant is more effective in bases having greater amountsof titanium dioxide (TiO₂), due to the fact that TiO₂ has alight-scattering effect.

The neutral paint colorant formed as described above is generally moreeffective for lighter (higher value) paint colors, i.e., the upper halfof the theoretical color space. In darker (lower value) regions of thecolor space, the paint is less sensitive to the addition of the neutralcolorant, requiring greater amounts of the neutral colorant to be addedto reduce the paint's chroma. Also, in the darker portion of the colorspace, the neutral paint undesirably tends to turn brown. It has beenfound that, in the darker regions of color space, the chroma of paintcan be more easily and effectively decreased, without appreciablyvarying the paint's hue or value, by simply adding black paints havingappropriate values (lightness levels). FIG. 6 illustrates this concept.Line 44 represents a uniform value within the darker region of the hueplane. Consider a paint color on line 44. The hue of this paint colormay be decreased, i.e., shifted to the left along line 44, by adding ablack paint, the black paint having the same value (lightness) as thecolors represented by line 44. The black paint comprises a blackcolorant blended with the same type of paint base as the paintsrepresented by line 44.

The neutral colorant of the invention has been found to be effectivethroughout virtually all of the upper half of the color space, within avalue range of 40-95. At the lower end of the value range, the neutralcolorant is especially effective at values above 50, more effective atvalues above 52, and even more effective at values above 55. At theupper end of the value range, the neutral colorant is especiallyeffective at values below 94. In certain regions, however, addition ofthe neutral colorant has been found not to produce the desired effect.In particular, in the less chromatic portions of the yellow-green andgreen-blue hues, the addition of neutral colorant has been found toresult in an undesirable hue shift. In particular, in these narrowregions of the color space the addition of the neutral colorant causesthe paint to turn brown. To compensate, the color can be modified toregain its intended perceptual appearance by adding some blue-shadeblack colorant to the produced paint. Also, in the more chromaticportions of the yellow hues, the addition of the neutral colorant hasbeen found to turn the paint green. To compensate, the color can bemodified to regain its intended perceptual appearance by addingyellow-oxide colorant to the paint.

Those skilled in the art will readily appreciate from the teachingsherein that a neutral colorant can be created that, when added to apaint, modifies one of the hue, value, and chroma of the paint whilemaintaining one or both of the other two of such color attributessubstantially constant. For example, a neutral colorant can be createdthat, when added to a paint, modifies the paint's value whilemaintaining the paint's hue and chroma substantially constant. Or, forexample, a neutral colorant can be created that, when added to a paint,modifies the paint's hue while maintaining the paint's value and chromasubstantially constant.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. Thus, it is intended that the scope of the present inventionherein disclosed should not be limited by the particular disclosedembodiments described above, but should be determined only by a fairreading of the claims that follow.

What is claimed is:
 1. A paint colorant comprising: 6.3% to 7.7% ColorIndex Pigment Yellow 42; 2.16% to 2.64% Color Index Pigment Red 101; and3.6% to 4.4% Color Index Pigment Black
 7. 2. The colorant of claim 1,comprising: 7.0% Color Index Pigment Yellow 42; 2.4% Color Index PigmentRed 101; and 4.0% Color Index Pigment Black
 7. 3. A method of producinga neutral paint colorant, comprising the steps of: blending Color IndexPigment Yellow 42, Color Index Pigment Red 101, and Color Index PigmentBlack 7 together to form a pigment mixture; and blending said pigmentmixture into a grinding liquid to form a paint colorant; wherein saidpaint colorant has a composition of 6.3%-7.7% Color Index Pigment Yellow42, 2.16%-2.64% Color Index Pigment Red 101, and 3.6%-4.4% Color IndexPigment Black
 7. 4. The method of claim 3, wherein said paint coloranthas a composition of 7.0% Color Index Pigment Yellow 42, 2.4% ColorIndex Pigment Red 101, and 4.0% Color Index Pigment Black 7.